Date of Award
2026
Document Type
Open Access Master's Thesis
Degree Name
Master of Science in Geology (MS)
Administrative Home Department
Department of Geological and Mining Engineering and Sciences
Advisor 1
James M. DeGraff
Committee Member 1
Chad D. Deering
Committee Member 2
Jeremy M. Shannon
Abstract
The Keweenaw fault is a crustal-scale fault spatially associated with Mesoproterozoic rocks of the Midcontinent Rift System. Along the fault, older Portage Lake Volcanics have been thrust southeastward over younger Jacobsville sandstone. Ideas on the fault’s origin, from oldest to most recent, include that it is: (1) a reverse fault, (2) a normal fault formed during midcontinent rifting that was reactivated and inverted to a reverse fault during the Grenville orogeny, and (3) a detached thrust fault system initiated during the Grenville orogeny.
This thesis is based on a U.S. Geological Survey EdMap grant to remap a portion of the Keweenaw fault between Mohawk and Hancock, MI in the Upper Peninsula of Michigan. Over two field seasons (2021-2022), detailed mapping was done to better define geologic relationships and to collect structural data, such as bedding attitudes and fault-slip indicators, for subsequent fold and fault analysis. As in previous EdMap projects, the Keweenaw fault is revealed to be a network of connected fault segments that collectively exhibit northwest-side-up reverse dip slip and dextral strike slip. The ratio of net dip-to-strike slip in the study area is about 1:1, which differs from a 1:2 ratio for previous EdMap areas to the northeast. This difference likely results from the change in angle between local fault system strike and expected direction of shortening in the region due to the Grenville orogeny. Cross-sections constructed to model subsurface geometry reveal broad open fault-bend folding in the hanging walls of the main fault segments and a gentle syncline-anticline in footwall Jacobsville Sandstone. The segmented fault pattern, cross-sectional modeling, fold and fault analysis indicate that the Keweenaw fault system formed in a compressive stress regime related to the Grenville orogeny.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Langfield, Katherine M., "SLIP KINEMATICS AND STRUCTURAL ANALYSIS OF THE KEWEENAW FAULT SYSTEM FROM LAKE LINDEN TO HANCOCK, MICHIGAN", Open Access Master's Thesis, Michigan Technological University, 2026.
https://digitalcommons.mtu.edu/etdr/2200